Theresa May's communications director has hit out at "fake news" after a claim about the cost of post-Brexit blue British passports was shared tens of thousands of times on Twitter.
Robbie Gibb said deliberately misrepresenting government policies "harms our democracy".
Ex-Dragon's Den panellist James Caan had shared claims the passports would cost £500m but later withdrew them.
The new passports will be issued from October 2019.
The redesign, which happens routinely every five years, will come as part of a £490m contract which also includes printing and assembling passports and runs for 11 and a half years.
But Mr Caan had claimed it would cost £500m just to change the colour.
The row came after Environment Secretary Michael Gove last month hit out at social media users who wrongly claimed MPs voted against treating animals as sentient beings.
Mr Gibb tweeted: "Fake news harms our democracy. Those who would deliberately misrepresent public policy for political gain - be it passports or animal sentience - should be called out."
Mr Caan's original tweet was shared more than 27,000 times by Saturday evening.
Mrs May has hailed the move to bring back blue travel documents as an expression of the UK's post-Brexit "sovereignty and independence", although Nicola Sturgeon described it as "insular, inward looking, nonsense".
The European Parliament's chief Brexit coordinator Guy Verhofstadt pointed out that Britain could have chosen to have a blue passport while remaining a member of the EU.
There is no Brussels regulation which states that EU countries' passports have to be a certain colour, simply a legally non-binding European Council resolution from 1981 which recommends burgundy red, reports BBC.